vim - vim 脚本中的 ".="是什么意思？

Question

我经常看到对“let s.='something'”形式的变量的赋值这是我一直在努力理解的vim脚本中的特定代码:

let s .= '%' . i . 'T'
let s .= (i == t ? '%1*' : '%2*')
let s .= ' '
let s .= i . ':'
let s .= winnr . '/' . tabpagewinnr(i,'$')
let s .= ' %*'
let s .= (i == t ? '%#TabLineSel#' : '%#TabLine#')

该代码将选项卡编号( i )和视口(viewport)编号( winnr 的 tabpagewinnr(i,'$') )添加到选项卡名称中，使其看起来像“1:2/4 缓冲区名称”。从外观上看， .=操作似乎正在向 s 添加内容.但是，我不明白前两行是做什么的。任何帮助表示赞赏。

Answer 1

vim的online help是你的 friend :

:h .=

 :let {var} .= {expr1}    Like ":let {var} = {var} . {expr1}".

:h expr-.

 expr6 .   expr6 ..   String concatenation

:h expr1 (嗯 - 这有点难找):

 expr2 ? expr1 : expr1

 The expression before the '?' is evaluated to a number.  If it evaluates to TRUE, the result is the value of the expression between the '?' and ':', otherwise the result is the value of the expression after the ':'.
 Example:
   :echo lnum == 1 ? "top" : lnum

  Since the first expression is an "expr2", it cannot contain another ?:.  The
  other two expressions can, thus allow for recursive use of ?:.
  Example:
    :echo lnum == 1 ? "top" : lnum == 1000 ? "last" : lnum

  To keep this readable, using |line-continuation| is suggested:
    :echo lnum == 1
    :\  ? "top"
    :\  : lnum == 1000
    :\      ? "last"
    :\      : lnum

  You should always put a space before the ':', otherwise it can be mistaken for
  use in a variable such as "a:1".